This disclosure relates to memory circuits.
Technologies have been proposed to provide low cost, low power electronic devices for widespread use, for example in order to add an electronic processing capability to items which previously had no such capability. An example relates to the so-called Internet of Things (IoT) in which devices which previously had no processing or networking capability are given such a capability. Another example relates to applications such as “smart” labelling of products in which a stick-on electronic circuit provides the function of an intelligent product label, for example being sensitive to the storage conditions or current price of the product.
The field of “printed electronics” is being developed to enable the low cost production of this type of device. In some examples, entire circuits including various circuit elements are printed onto a substrate (such as a flexible plastic or paper substrate) using, for example, an ink-jet printer mechanism. In other examples, a circuit is fabricated using a slightly more conventional fabrication process but is made “print-programmable” by providing externally accessible regions onto which a user can apply (for example, print) conductive material in order to connect a pair of conductors at the region and change the state of the circuitry. An application of this technique is in a circuit comprising an array of programmable memory elements fabricated on a substrate, each memory element having one or more processable regions which, when processed by an external process in which a material (such as a conductive material or ink) is applied to at least partially cover one or more of the regions, are configured to program that memory element to one of multiple states.